Small vessel thrombosis is one of the major hurdles when using decellularized extracellular matrix (ECM) as a tissue/organ engineering scaffold. Heparin is often immobilized onto the ECM to provide anticoagulant activity. However, strategies to immobilize heparin onto ECM involve chemical crosslinking, which increases the mechanical stiffness and alters the ultrastructure of the ECM. It is important for the ECM to maintain its native mechanical properties and structure for its proper function.